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Thread: Question regarding high-power EPs

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    Default Question regarding high-power EPs



    I am looking into getting a higher magnification EP for my AD8 but I am confused as what to consider for the EP. My AD8 has a focal ratio of f/5.91, 203mm aperture, and a focal length of 1200mm. I have seen people talk about not getting an EP with a lower focal length than you focal ratio and I have seen the exit pupil size topic used as well. Which method would be better for selecting an EP? I would like to have a an eyepiece with more magnification than my 9mm by the time Mars comes into opposition.
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    Default Re: Question regarding high-power EPs

    I'm not so much into the math part of determining and buying EPs, but for my XT8 the 6mm is quite doable when I want that level of magnification.
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    Default Re: Question regarding high-power EPs

    Quote Originally Posted by Newt Reno View Post
    I'm not so much into the math part of determining and buying EPs, but for my XT8 the 6mm is quite doable when I want that level of magnification.
    I was thinking along the lines of a 6mm for it.
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    Default Re: Question regarding high-power EPs

    I have the Orion 6mm Edge-on Planetary and it might be a little spendy compared to some available 6mm EPs, but it is solid and Ive had very good views through it when the sky allows; it has seen use in my XT8 and my 150mm mak.

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    Default Re: Question regarding high-power EPs

    this handy calculator might help give some insight into the issue.....I was out with my scope tonight, and the 6mm was pushing the seeing limits.....things get pretty swimmy looking once you get close to the edge.... The atmospheric conditions at high power magnification nearly always make the rules of what is the max......I didn't try the 9mm, but it probably would have give a more stable image and about the same detail tonight.....If you select an EP that is right on the threshold of your scopes theoretical power limit, it probably will be pretty disappointing and collect a lot of dust....Depending on your location, those super clear nights of excellent seeing don't really come around very often at all.......That's why I bought the 6mm instead of a 5mm or 3mm...For my scope, it would be more forgiving, thus, more useful more often... Here's a link to the calculator---- N.A.A. Telescope Math Calculator
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    Default Re: Question regarding high-power EPs

    Thank you for you help, I'll be looking at a 6mm EP soon. But first order of business is to get a good mount for my Celestron 15x70s.
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    Default Re: Question regarding high-power EPs

    Quote Originally Posted by David_MC View Post
    I am looking into getting a higher magnification EP for my AD8 but I am confused as what to consider for the EP. My AD8 has a focal ratio of f/5.91, 203mm aperture, and a focal length of 1200mm. I have seen people talk about not getting an EP with a lower focal length than you focal ratio and I have seen the exit pupil size topic used as well. Which method would be better for selecting an EP? I would like to have a an eyepiece with more magnification than my 9mm by the time Mars comes into opposition.
    I intend to use my 1.25"-12mm Celestron XCel LX with my GSO 2" Barlow to get the high power views, when sky conditions allow, with my new SW 8" Dob !

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    Default Re: Question regarding high-power EPs

    Quote Originally Posted by David_MC View Post
    Thank you for you help, I'll be looking at a 6mm EP soon. But first order of business is to get a good mount for my Celestron 15x70s.
    David... I think 6mm will be perfect. As others mentioned, a good rule of thumb is to keep the focal length of your eyepieces no shorter than your focal ratio expressed in millimeters. In the case of my f/4.7 Dob, 5mm is my max. However, it takes pretty good seeing conditions to use it.

    Another point I often make is that faster scopes (8"+ Dobs, etc) perform much better above 100x with multi-lens, multi-cell eyepieces. I have had much success with the Baader Hyperion series of eyepieces. They're a bit pricey (~$130), but very versatile and worth the expense IMHO.

    Regarding a mount for your 15x70's...
    For a couple of years, I used a very heavy duty tripod (built to hold a movie camera) for my 25x70's. For Christmas, my lovely wife bought me one of these: Big Binoculars - Monopods

    I couldn't be happier. It is easily adjustable and the pistol grip head is very handy for views around zenith. Be sure to order the heavy duty L-adapter too, as the plastic one that comes with the Celestron binoculars will oscillate terribly.

    Clear Skies
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    Default Re: Question regarding high-power EPs

    I was considering the Orion Paragon binocular mount since I already have a very sturdy photographic tripod with a removable pan head.
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    Default Re: Question regarding high-power EPs

    6mm works fine most of the time on my 8" dob (I barlow my 12mm). I've tried 5mm and it's rare that works well (240x). There are lots of times that the barlowed 12mm doesn't work well. Depends on conditions.
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